Method suitable for on-site analysis of valence state of thallium in water

Abstract

The invention discloses a method suitable for on-site analysis of the valence state of thallium in water. The method comprises the following operation steps: step 1, collecting and separating a water sample; step 2, acidizing treatment; 3, Tl (I) and Tl (III) are separated; 4, total thallium is measured; step 5, Tl (I) determination; the invention relates to the technical field of atomic spectrum metal element analysis, and the method has the beneficial effects that by combining an electrochemical separation technology with a Chelex-100 solid-phase extraction column and cooperating with a portable liquid cathode glow discharge thallium measurement instrument, high-sensitivity field detection of Tl (I) and Tl (III) is realized, the detection limit is lower than 1.0 g / L, and the repeatability is RSDlt; the analysis period of a single sample is less than or equal to 30 minutes, the weight of equipment is only 5kg, battery power supply is supported, and acidification-separation-detection integrated operation can be completed outdoors without professional laboratory conditions.

Description

Technical Field

[0001] This invention relates to the field of atomic spectroscopy metal elemental analysis technology, and in particular to a method for on-site analysis of the valence state of thallium in water. Background Technology

[0002] The liquid cathode glow discharge thallium analyzer can be used to determine thallium in various aquatic environmental samples. This instrument applies a voltage of several hundred to several thousand volts between the metal anode and the sample solution cathode, causing ionization of the gas between the electrodes and forming a micro-plasma. During the discharge, thallium ions volatilize or sputter into the micro-plasma, are thermally excited, and produce an emission spectrum. The quantitative detection of the analyte is achieved through the characteristic radiation of thallium. This detection process does not distinguish the valence state of thallium; it measures the total amount of thallium.

[0003] Thallium pollutants in aquatic environments are mainly composed of Tl(I) and Tl(III), but current methods for determining thallium in aquatic environments primarily focus on the determination of total Tl. However, Tl(I) and Tl(III) differ significantly in their properties and toxicity, necessitating the development of a method for analyzing the valence states of Tl(I) and Tl(III). Currently, liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) is used for analyzing the valence states of Tl(I) and Tl(III) in water. However, this method is limited by instrument hardware and can only be used in the laboratory, not for field analysis. Furthermore, its overall analytical efficiency is low, making it difficult to meet the timeliness requirements of emergency analysis. Therefore, this case study was developed to address these issues. Summary of the Invention

[0004] The technical solution of the present invention to achieve the above objectives is as follows: A method for on-site analysis of the valence state of thallium in water, comprising the following steps: Step 1: Water sample collection and aliquoting. Collect 100ml of water sample and divide it into two equal portions of 50ml each. Step 2: Acidification treatment, add concentrated nitric acid to both water samples to a volume concentration of 1%; Step 3: Separate Tl(Ⅰ) and Tl(Ⅲ). Pass one portion of the acidified water sample through a Chelex-100 solid phase extraction column at a flow rate of 5 ml / min. Tl(Ⅲ) is retained on the column. Collect the eluent to obtain the Tl(Ⅰ) solution. Step 4: Total thallium determination. The emission intensity of the unfiltered water sample was directly measured using a portable liquid cathode glow discharge thallium analyzer to obtain the total Tl content. Step 5: Tl(Ⅰ) determination: Measure the emission intensity of the effluent after passing through the column to obtain the Tl(Ⅰ) content; Step 6: Calculate Tl(Ⅲ). The difference between the total Tl and Tl(Ⅰ) content is the Tl(Ⅲ) content.

[0005] Preferably, step 1 further includes Blank experiment: Insert one ultrapure water blank for every 10 samples, and the blank value should be ≤0.5μg / L; Parallel sample testing: The same water sample was tested repeatedly 5 times, and the relative standard deviation (RSD) was ≤5%; Standard reference comparison: Insert 50 μg / L thallium standard solution into each batch of analysis, and the deviation between the measured value and the standard value should be ≤5%.

[0006] Preferably, in step 3, the detection parameters of the portable liquid cathode glow discharge thallium detector are: a voltage of 200-800V applied between the anode and the liquid cathode, a discharge time of 1.5 minutes / time, and a spectral acquisition wavelength of 190.856nm.

[0007] Preferably, in step 3, the preparation of the Chelex-100 solid-phase extraction column is as follows: a sieve plate and glass wool are placed in an empty packed column, 20-500 mg of Chelex 100 ion exchange resin is added, and then glass wool and a sieve plate are placed on top and compacted appropriately.

[0008] 5. A method for on-site analysis of thallium valence state in water according to claim 4, characterized in that, in step 3, the flow rate control of the separation step is achieved by a peristaltic pump, with a flow rate error of ±0.2 ml / min.

[0009] Preferably, in step 4, the thallium discharge detector includes a metal heat sink, a solid metal anode is disposed on the metal heat sink, a graphite auxiliary cathode is disposed on the solid metal anode, the distance between the graphite auxiliary cathode and the solid metal anode is 3-5mm, a power supply is disposed on the graphite auxiliary cathode and the solid metal anode, the power supply is connected to the graphite auxiliary cathode and the solid metal anode through wires, the graphite auxiliary cathode and the solid metal anode are vertically arranged in a detection box, a photodetector is disposed on the detection box, a switching valve is disposed on the detection box, an injection pump and a test liquid bottle are disposed on the switching valve, and a waste liquid pipe is disposed on the detection box.

[0010] Preferably, in step 6, after use, the portable liquid cathode glow discharge thallium analyzer and solid phase extraction column are cleaned and maintained to ensure accuracy and reliability for the next use.

[0011] This invention provides a method for on-site analysis of thallium valence states in water. By combining electrochemical separation technology with a Chelex-100 solid-phase extraction column and a portable liquid cathode glow discharge thallium analyzer, it achieves highly sensitive on-site detection of Tl(I) and Tl(III), with detection limits below 1.0 µg / L, repeatability RSD < 5%, single-sample analysis cycle ≤ 30 minutes, and the device weighs only 5 kg and is battery powered. It can perform integrated acidification-separation-detection operations in the field without the need for professional laboratory conditions. Compared with laboratory methods such as liquid chromatography-ICP-MS, this invention reduces reagent consumption by 80%, waste liquid generation by < 5 ml / sample, and operating costs by more than 90%, making it particularly suitable for emergency monitoring of sudden pollution incidents and water quality screening in remote areas. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the experimental apparatus for the on-site analysis of the valence state of thallium in water, as described in this invention.

[0013] Figure 2 This is a schematic diagram of the preparation of a solid-phase extraction column for a method for on-site analysis of the valence state of thallium in water, as described in this invention. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings, and embodiments will be provided. Therefore, this application protects the following: Assembling an electrochemical separation device: fixing a platinum-iridium alloy anode (coated with a diamond film) to a metal heat sink, maintaining a 4mm gap with the graphite auxiliary cathode, and connecting to a 500V adjustable power supply; calibrating the photodetector: setting the wavelength acquisition range to 190-200nm, the light signal acquisition angle to 45°, and connecting to an external data processing system; collecting 100mL of water sample and dividing it into two portions, adding concentrated nitric acid to each portion to a volume concentration of 1%, and letting it stand for 10 minutes for acidification; total thallium determination: directly taking 50mL of acidified water sample, inputting it into the separation chamber at a flow rate of 2ml / min through a syringe pump, applying an 800V voltage for electrochemical separation, and simultaneously recording the spectral signal of total thallium using the photodetector; Tl(Ⅰ) separation: the other acidified portion Water samples were filtered through a Chelex-100 solid-phase extraction column (200 mg resin). Tl(III) was adsorbed onto the column, and the effluent was collected to obtain Tl(I) solution. The emission intensity of the total thallium solution and the Tl(I) solution was determined using a portable thallium analyzer. Instrument parameters: voltage 500V, discharge time 1.5 minutes / cycle, detection limit ≤1.0 μg / L. The concentration was calculated using the calibration curve C=0.02I+1.5. The difference between total thallium and Tl(I) was the content of Tl(III). Each batch of samples was verified by inserting a 50 μg / L standard solution, with an allowable deviation ≤5%. Blank experiment: every 10 samples were inserted with an ultrapure water blank, with a blank value ≤0.5 μg / L. Parallel sample determination: 6 replicates with RSD ≤5%.

[0015] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for on-site analysis of the valence state of thallium in water, characterized in that, The following steps are included: Step 1: Water sample collection and aliquoting. Collect 100ml of water sample and divide it into two equal portions of 50ml each. Step 2: Acidification treatment, add concentrated nitric acid to both water samples to a volume concentration of 1%; Step 3: Separate Tl(Ⅰ) and Tl(Ⅲ). Pass one portion of the acidified water sample through a Chelex-100 solid phase extraction column at a flow rate of 5 ml / min. Tl(Ⅲ) is retained on the column. Collect the eluent to obtain the Tl(Ⅰ) solution. Step 4: Total thallium determination. The emission intensity of the unfiltered water sample was directly measured using a portable liquid cathode glow discharge thallium analyzer to obtain the total Tl content. Step 5: Tl(Ⅰ) determination: Measure the emission intensity of the effluent after passing through the column to obtain the Tl(Ⅰ) content; Step 6: Calculate Tl(Ⅲ). The difference between the total Tl and Tl(Ⅰ) content is the Tl(Ⅲ) content.

2. The method for on-site analysis of the valence state of thallium in water according to claim 1, characterized in that, Step 1 also includes Blank experiment: Insert one ultrapure water blank for every 10 samples, and the blank value should be ≤0.5μg / L; Parallel sample testing: The same water sample was tested repeatedly 5 times, and the relative standard deviation (RSD) was ≤5%; Standard reference comparison: Insert 50 μg / L thallium standard solution into each batch of analysis, and the deviation between the measured value and the standard value should be ≤5%.

3. The method for on-site analysis of the valence state of thallium in water according to claim 2, characterized in that, In step 3, the detection parameters of the portable liquid cathode glow discharge thallium detector are as follows: a voltage of 200-800V is applied between the anode and the liquid cathode, the discharge time is 1.5 minutes / time, and the spectral acquisition wavelength is 190.856nm.

4. The method for on-site analysis of the valence state of thallium in water according to claim 3, characterized in that, Step 3, preparation of the Chelex-100 solid-phase extraction column: Place a sieve plate and glass wool in an empty packed column, add 20-500 mg of Chelex 100 ion exchange resin, and then place glass wool and sieve plate on top, and compact appropriately.

5. The method for on-site analysis of the valence state of thallium in water according to claim 4, characterized in that, In step 3, the flow rate control of the separation step is achieved by a peristaltic pump, with a flow rate error of ±0.2 ml / min.

6. The method for on-site analysis of the valence state of thallium in water according to claim 5, characterized in that, In step 4, the thallium discharge detector includes a metal heat sink, on which a solid metal anode is mounted. A graphite auxiliary cathode is mounted on the solid metal anode, with a distance of 3-5 mm between the graphite auxiliary cathode and the solid metal anode. A power supply is mounted on the graphite auxiliary cathode and the solid metal anode, and the power supply is connected to the graphite auxiliary cathode and the solid metal anode via wires. The graphite auxiliary cathode and the solid metal anode are vertically mounted in a detection chamber, which is equipped with a photodetector, a switching valve, an injection pump, a test solution bottle, and a waste liquid pipe.

7. The method for on-site analysis of the valence state of thallium in water according to claim 6, characterized in that, After use, step 6 involves cleaning and maintaining the portable liquid cathode glow discharge thallium analyzer and solid phase extraction column to ensure accuracy and reliability for future use.

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